Heretofore, in a vehicle such as a minivan or an estate car (so-called one-box car), a sliding door (opening-closing body) that slides in a front-rear direction of the vehicle is provided on a side portion of a vehicle body. This allows getting on and off the vehicle or loading and unloading of a burden to be carried out easily from a large opening portion that is formed on the side portion of the vehicle body. Since weight of the sliding door is heavy, a power sliding door device capable of automatically opening and closing the sliding door is mounted on the vehicle.
In the power sliding door device, one end of a cable the other end of which is connected to the sliding door from a front-rear direction of the vehicle is introduced to a driving unit via inversion pulleys provided at both ends of a guide rail fixed to a vehicle body. The one end of the cable is wound around a drum of the driving unit. By rotating the drum by means of a motor, the sliding door is pulled by the cable to open and close the opening portion.
In the cable type power sliding door device as described above, the sliding door is guided by a curved portion of the guide rail and is drawn into the inside of the vehicle body by strong force. For this reason, the cable extends due to long-term usage, whereby a path length of the cable gets elongated. For example, in a driving unit described in Patent Document 1, in order to absorb change in the path length of a cable, a pair of tensioner mechanisms is provided in a case so as to correspond to open-side and close-side cables. This causes predetermined tension to be applied to each of the cables, thereby eliminating slack of each of the cables.